Paper navigational charts used by pilots of modern aircraft are being replaced by "electronic maps" in the form of digitally stored data systems.
In digitally stored data systems, paper charts are digitally reproduced and stored in binary form in bulk memory. In order to achieve an image resolution comparable to that of otherwise used optically based film strip systems, a significant amount of digital data must be collected and stored in what amounts to a vast amount of memory in the form of a disc (optical or magnetic) or a solid state read only memory (ROM).
Digital image data, as in the case of paper navigational charts, is highly correlated and thus contains a significant amount of redundant data. Accordingly, the digital image data is usually compressed. Most prior art compression methods store only non-redundant data, thus reducing storage requirements and bit rates. These methods result in degradation of a reconstituted image due to losses experienced during compression.
Accordingly, it is the object of the present invention to reduce the amount of digital data required to be stored without degrading the reconstituted image.